CN113945545A - SPR sensor based on defect disc coupling nanorod structure - Google Patents
SPR sensor based on defect disc coupling nanorod structure Download PDFInfo
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Abstract
The invention discloses a defect-based disc coupling nanorod structure SPR sensor, which comprises a silicon dioxide substrate and at least one metal nano unit arranged on the silicon dioxide substrate; each metal nano unit consists of a metal nano defect disc and a metal nano rod; a gap is formed between the metal nanometer defect disc and the metal nanometer rod; the metal nanometer defect disc is a round disc with a rectangular notch at the edge; the metal nano-rod is rectangular; the rectangular notch on the metal nanometer defect disc faces to the direction of the metal nano-rod, and the center line of the wide side of the rectangular notch is perpendicular to the center line of the wide side of the metal nano-rod. The invention generates dipoles through the metal nanometer defect disc and the metal nanometer rods, and the two dipoles are mutually coupled to generate a surface plasma resonance peak. By changing the geometric parameters of the metal nanometer unit, the regulation and control of the resonance intensity and the resonance wavelength position of the surface plasma resonance can be realized, and high sensitivity can be obtained.
Description
Technical Field
The invention relates to the technical field of sensors, in particular to a defect-based disc coupling nanorod structure SPR sensor.
Background
Surface Plasmon Resonance (SPR) is a physical optical phenomenon that results from the interaction of an incident light wave and free electrons on the surface of a metal conductor. Surface plasmon resonance has two distinct advantages: one is that the material on the metal surface is particularly sensitive, and the change of the surface plasma resonance frequency can be caused by the absorption of trace molecules; the other produces a significantly localized field enhancement at the metal surface. The SPR sensor is a sensor implemented using the principle of surface plasmon resonance, and has important applications in the fields of chemical analysis, biological monitoring, and the like. Currently, SPR sensors include an intensity modulation type SPR sensor, an angle modulation type SPR sensor, and a phase modulation type SPR sensor, in which the intensity modulation type SPR sensor has a disadvantage that accuracy of a result is easily affected by a change in intensity of a light source, and the angle modulation type SPR sensor has a disadvantage that a dynamic range of detection is small, and the phase modulation type SPR sensor has a disadvantage that a system is complicated and data processing is troublesome.
Disclosure of Invention
The invention aims to solve the problems of easy oxidation, poor stability and low sensitivity of the conventional SPR sensor structure and provides a defect-based disc coupling nanorod structure SPR sensor.
In order to solve the problems, the invention is realized by the following technical scheme:
the SPR sensor based on the defect disc coupling nanorod structure comprises a silicon dioxide substrate and at least one metal nano unit arranged on the silicon dioxide substrate; each metal nano unit consists of a metal nano defect disc and a metal nano rod; a gap is formed between the metal nanometer defect disc and the metal nanometer rod; the metal nanometer defect disc is a round disc with a rectangular notch at the edge; the metal nano-rod is rectangular; the rectangular notch on the metal nanometer defect disc faces to the direction of the metal nano-rod, and the center line of the wide side of the rectangular notch is perpendicular to the center line of the wide side of the metal nano-rod.
In the above scheme, the line extending from the center of the wide side or the extended line from the center of the wide side of the rectangular notch of the metal nano-defect disc passes through the center of the metal nano-defect disc.
In the above scheme, the length of the rectangular gap of the metal nano-defect disk is equal to the radius of the metal nano-defect disk.
In the scheme, the thicknesses h of the metal nanometer defect disc and the metal nanometer rod are equal.
In the scheme, the metal nanometer defect disc and the metal nanometer rod are made of gold.
In the scheme, the resonant wavelength of the metal nano unit is regulated and controlled by changing the width of the metal nano defect disc, the metal nano rod, the rectangular notch, the width d of the metal nano rod and/or the length l of the metal nano rod.
In the above scheme, when the number of the metal nano-units is more than 2, the metal nano-units are periodically arranged on the silicon dioxide substrate.
Compared with the prior art, the metal nano defect disc and the metal nano rod generate dipoles, and the two dipoles are coupled with each other to generate a surface plasma resonance peak. By changing the geometric parameters of the metal nanometer unit, the regulation and control of the resonance intensity and the resonance wavelength position of the surface plasma resonance can be realized, and high sensitivity can be obtained. Experimental results show that the maximum refractive index sensitivity (S) of the invention to a medium with a refractive index of 1.00-1.08 in a wavelength band of 1000-1600 nm is 470 +/-10 nm/RIU. The invention adopts the wavelength modulation type SPR sensor, and has the advantages of high sensitivity, good stability, large dynamic range and suitability for various coupling modes. Therefore, the gold nano metal structure has the characteristics of stability, difficult oxidation and excellent optical property. The invention has potential application prospect in the aspects of biosensors such as environment refractive index and the like and micro-nano photonic devices.
Drawings
FIG. 1 is a schematic structural diagram of a SPR sensor based on a defective disc coupled nanorod structure.
Fig. 2 is a graph of transmission spectra of a metal nano-defect disc alone, a metal nanorod alone, and a metal nano-defect disc and a metal nanorod simultaneously.
FIG. 3 is a graph showing the transmission spectra obtained by varying the distances g (10nm, 15nm, 20nm, 25nm, 30nm) between the metal nano-defect disks and the metal nanorods.
FIG. 4 is a graph of transmission spectra obtained by varying the rectangular notch width w (30nm, 40nm, 50nm, 60nm) of a metal nano-defect disc.
FIG. 5 is a graph of transmission spectra obtained by varying the widths d (15nm, 20nm, 25nm, 30nm, 35nm) of the metal nanorods.
FIG. 6 is a graph of transmission spectra obtained by varying the lengths l (220nm, 230nm, 240nm, 250nm, 260nm) of metal nanorods.
Fig. 7 is a graph of the transmission characteristics of the sensor obtained by varying the ambient refractive index n (1.00, 1.02, 1.04, 1.06, 1.08).
Fig. 8 is a graph of refractive index n (1.00, 1.02, 1.04, 1.06, 1.08) versus resonant wavelength.
The following are marked in the figure: 1. a silicon dioxide substrate; 2-1, metal nanometer defect disc; 2-2 and metal nano-rods.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to specific examples.
Referring to fig. 1, a defect-based disc-coupled nanorod structure SPR sensor includes a silicon dioxide substrate 1, and at least one metal nano-unit disposed on the silicon dioxide substrate 1. When a plurality of metal nano-units are present on the silicon dioxide substrate 1, the metal nano-units are arranged periodically on the silicon dioxide substrate 1. Each metal nano unit consists of a metal nano defect disc 2-1 and a metal nano rod 2-2. A gap is formed between the metal nanometer defect disc 2-1 and the metal nanometer rod 2-2. The metal nanometer defect disc 2-1 is a round disc with rectangular gaps at the edges. The metal nano-rod 2-2 is rectangular. The rectangular notch on the metal nanometer defect disc 2-1 faces to the direction of the metal nanometer rod 2-2, and the center line of the wide side of the rectangular notch is vertical to the center line of the wide side of the metal nanometer rod 2-2. When polarized light is incident to the surface of the metal nano unit, the metal nano defect disc 2-1 and the metal nano rod 2-2 are dipoles, and the two dipoles are mutually coupled to generate SPR resonance. The plane wave vertically enters the metal surface downwards along the positive direction of the Z axis of the SPR sensor, is polarized along the Y direction, the X direction and the Y direction are set as periodic boundary conditions, and the Z direction is set as absorption boundary conditions (PML) so as to ensure the continuous distribution of a medium on the boundary.
One end of a rectangular gap on the metal nano defect disc 2-1 is positioned in the middle of the metal nano defect disc 2-1, and the other end extends to the edge of the metal nano defect disc 2-1. The center line of the wide side of the rectangular notch can coincide with the diameter of the metal nano defect disc 2-1 and can also not coincide with the diameter of the metal nano defect disc 2-1. In the preferred embodiment of the invention, the center line of the wide side of the rectangular notch can coincide with the diameter of the metal nano-defect disc 2-1, i.e. the center line of the wide side of the rectangular notch or the extension line of the center line of the wide side passes through the center of the metal nano-defect disc 2-1. When the length of the rectangular gap is equal to or greater than the radius of the metal nano defect disc 2-1, the center line of the wide side of the rectangular gap passes through the center of the metal nano defect disc 2-1; when the length of the rectangular gap is smaller than the radius of the metal nano defect disc 2-1, the extension line of the center line of the wide side of the rectangular gap passes through the center of the metal nano defect disc 2-1. In the preferred embodiment of the invention, the length of the rectangular gap is equal to the radius of the metal nano-defect disc 2-1.
In the invention, gold is selected as the material of the metal film, namely the metal nanometer defect disc 2-1 and the metal nanometer rod 2-2. The thickness h of the metal nanometer defect disc 2-1 is 30nm consistent with that of the metal nanometer rod 2-2. The length r of the rectangular gap of the metal nanometer defect disc 2-1 is 130nm consistent with the radius of the metal nanometer defect disc 2-1, and the width w of the rectangular gap is 30 nm-60 nm. The width d of the metal nano rod 2-2 is 15 nm-35 nm, and the length l of the metal nano rod 2-2 is 220 nm-260 nm. The distance g between the metal nanometer defect disc 2-1 and the metal nanometer rod 2-2 is 10 nm-30 nm. The refractive index variation range of the surrounding environment is 1.00-1.08. In a preferred embodiment of the invention, the width w of the rectangular notch is 50 nm. The width d of the metal nanorod 2-2 is 25nm, and the length l of the metal nanorod 2-2 is 240 nm. The distance g between the metal nano-defect disc 2-1 and the metal nano-rod 2-2 is 20 nm.
FIG. 2 is a transmission spectrum curve of a silicon dioxide substrate 1 with a metal nano-defect disk 2-1, a metal nano-rod 2-2 and both the metal nano-defect disk 2-1 and the metal nano-rod 2-2 in a wavelength range of 1000nm to 1600 nm. As can be seen from the figure, resonance occurs only when the metal nano-defect disk 2-1 and the metal nanorods 2-2 are coupled while being disposed on the silicon dioxide substrate 1.
The geometrical parameters of the metal nano-unit are adjusted, namely the metal nano defect disc 2-1 and the metal nanorod 2-2 are changed, the width of the rectangular notch, the width d of the metal nanorod 2-2 and/or the length l of the metal nanorod 2-2 are/is changed (when the width d of the metal nanorod 2-2 is changed, the resonance intensity and the resonance wavelength position are simultaneously changed, and when the length l of the metal nanorod 2-2 is changed, the position of the resonance wavelength is changed), and the local surface plasmon resonance between the metal nano-particles can be changed due to the electric field coupling effect, so that the resonance wavelength, namely the resonance intensity or the resonance wavelength position of the spectrum of the metal nano-unit is changed, and meanwhile, the metal nano-unit has higher sensitivity to the ambient refractive index.
FIG. 3 is a transmission spectrum curve obtained by changing the distance g between the metal nano-defect disc 2-1 and the metal nanorod 2-2, the coupling distance g is increased from 10nm to 30nm in steps of 5nm, and it can be seen that the resonance wavelength is red-shifted with the increase of the distance g. Fig. 4 is a transmission spectrum curve obtained by changing the defect opening width w of the metal nano-defect disc 2-1, which is increased from 30nm to 60nm in steps of 10nm, and it can be seen that the resonance wavelength appears blue-shifted as the defect opening width w is increased. FIG. 5 is a transmission spectrum curve obtained by changing the width d of the metal nanorods 2-2, the width d is increased from 15nm to 35nm in 5nm steps, and it can be seen that the resonance wavelength appears blue-shifted as the width d is increased. FIG. 6 is a transmission spectrum curve obtained by changing the length l of the metal nanorod 2-2, the width l is from 220nm to 260nm in steps of 10nm, and it can be seen that the resonance wavelength appears red-shifted as the width l increases. The above results show that the resonance wavelength can be effectively tuned by changing the geometric parameters of the metal nano-unit.
Fig. 7 shows that the transmission characteristic curve of the sensor is obtained by changing the refractive index n of the surrounding environment, so that the refractive index n of the surrounding environment is increased from 1.00 to 1.08 in steps of 0.02, and as can be seen, the resonance peak appears to be obviously red-shifted along with the increase of the refractive index n. Fig. 8 is a graph of the relationship between different refractive indices n and resonance wavelength, based on which, according to the sensitivity (S) formula: s ═ d λ/dn (nm/RIU) represents the shift of the resonance wavelength due to the change in the refractive index of the medium, and the sensitivity at which the resonance peak was obtained was 470 ± 10 nm/RIU. The above results show that an optimal sensitivity can be obtained by reasonably setting the geometric parameters of the metal nano-unit.
It should be noted that, although the above-mentioned embodiments of the present invention are illustrative, the present invention is not limited thereto, and thus the present invention is not limited to the above-mentioned embodiments. Other embodiments, which can be made by those skilled in the art in light of the teachings of the present invention, are considered to be within the scope of the present invention without departing from its principles.
Claims (7)
1. The SPR sensor based on the defect disc coupling nanorod structure is characterized by comprising a silicon dioxide substrate (1) and at least one metal nano unit arranged on the silicon dioxide substrate (1); each metal nano unit consists of a metal nano defect disc (2-1) and a metal nano rod (2-2); a gap is formed between the metal nanometer defect disc (2-1) and the metal nanometer rod (2-2); the metal nanometer defect disc (2-1) is round with a rectangular notch at the edge; the metal nano rod (2-2) is rectangular; the rectangular notch on the metal nanometer defect disc (2-1) faces to the direction of the metal nanometer rod (2-2), and the center line of the wide side of the rectangular notch is vertical to the center line of the wide side of the metal nanometer rod (2-2).
2. The SPR sensor based on the defect disc coupling nanorod structure of claim 1, wherein a broadside center line of a rectangular notch of the metal nano-defect disc (2-1) or an extension line of the broadside center line passes through the center of the metal nano-defect disc (2-1).
3. The SPR sensor based on the defect disc coupling nanorod structure of claim 2, wherein the length of the rectangular gap of the metal nano-defect disc (2-1) is equal to the radius of the metal nano-defect disc (2-1).
4. The SPR sensor based on the defect disc coupling nanorod structure of claim 2, wherein the thicknesses h of the metal nanometer defect disc (2-1) and the metal nanorods (2-2) are equal.
5. The SPR sensor based on the defect disc coupling nanorod structure of claim 1, wherein the material of the metal nanometer defect disc (2-1) and the metal nanorods (2-2) is gold.
6. The SPR sensor based on the defect disc coupling nanorod structure of claim 1, wherein the tuning of the resonance wavelength of the metal nano-unit is achieved by changing the metal nano-defect disc (2-1) and the metal nanorods (2-2), the width of the rectangular gap, the width d of the metal nanorods (2-2) and/or the length l of the metal nanorods (2-2).
7. The SPR sensor based on the defective disc-coupled nanorod structure of claim 1, wherein when the number of the metal nano-units is more than 2, the metal nano-units are periodically arranged on the silicon dioxide substrate (1).
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| CN114966922A (en) * | 2022-05-18 | 2022-08-30 | 大连大学 | Plasmon amplitude tuner based on rhodium-silicon dioxide nano composite structure |
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| CN114966922A (en) * | 2022-05-18 | 2022-08-30 | 大连大学 | Plasmon amplitude tuner based on rhodium-silicon dioxide nano composite structure |
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